Let's start with the simple change and click on your system clock and select change date and time settings...

On the tab Internet Time select Change settings... and as a server, enter the name of your country's main pool, be.pool.ntp.org for Belgium. Press Update now to test it, and finally close all windows again.

At this point you're randomly picking an NTP server in your country for your weekly update. Let's improve this a bit by adding multiple servers.

Open an administrative command prompt and enter the following command (replace the server names by the list of your country, space separated, surrounded by double quotes):